This protocol will evaluate the safety and biologic efficacy of repeat administration of the recombinant adenovirus vector AdgvCFTR.10 to the airway epithelium of individuals with cystic fibrosis. Key elements of this study are: administration of the vector to more localized areas of the airways, more careful definition of the pharmacodynamics of expression of the normal CFTR cDNA, evaluation of this expression following repeat administration, and use of a more active promoter/enhancer in the expression cassette. Progress report and summary of findings: Parts A and C of the study have been completed. A total of fourteen patients were enrolled. Ten patients have received three administrations of the AdGVCFTR.10 vector; three patients have received two administrations of the AdGVCFTR.10 vector; and one patient has received one administration of the AdGVCFTR.10 vector. In part B, five individuals are projected to enroll, two of which have completed the study and have each had four administrations of the vector, one individual is currently enrolled. Patients continue to be followed as outpatients.